Hydrocarbon refrigerant compositions and uses thereof

ABSTRACT

The present invention relates to compositions for use in refrigeration and air-conditioning systems comprising at least one hydrocarbon, and which are also useful in systems employing a centrifugal compressor The are useful in processes for producing cooling or heat or as heat transfer fluids.

CROSS REFERENCE(S) TO RELATED APPLICATION(S)

This application claims the priority benefit of U.S. Provisional Application No. 60/584,785, filed Jun. 29, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions for use in refrigeration and air-conditioning systems comprising at least one hydrocarbon. Further, the present invention relates to compositions for use in refrigeration and air-conditioning systems employing a centrifugal compressor comprising at least one hydrocarbon. The compositions of the present invention are useful in processes for producing refrigeration or heat or as heat transfer fluids.

2. Description of Related Art

The refrigeration industry has been working for the past few decades to find replacement refrigerants for the ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. The new HFC refrigerants, HFC-134a being the most widely used at this time, have zero ozone depletion potential and thus are not affected by the current regulatory phase-out as a result of the Montreal Protocol.

Further, environmental regulations may ultimately cause global phase-out of certain HFC refrigerants. Currently, the automobile industry is facing regulations relating to global warming potential (GWP) for refrigerants used in mobile air-conditioning. Therefore, there is a great current need to identify new refrigerants with reduced GWP for the automobile air-conditioning market. Should the regulations be more broadly applied in the future, an even greater need will be felt for low GWP refrigerants that can be used in all areas of the refrigeration and air-conditioning industry.

Currently proposed replacement refrigerants for HFC-134a include HFC-152a, pure hydrocarbons such as butane or propane, or “natural” refrigerants such as CO₂ or ammonia. Many of these suggested replacements are toxic, flammable, and/or have low energy efficiency. Therefore, new alternatives are constantly being sought.

The present invention provides refrigerant compositions and heat transfer fluids having unique characteristics to meet the demands of low or zero ozone depletion potential, and lower GWP.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to refrigerant or heat transfer fluid composition comprising at least one hydrocarbon selected from the group consisting of:

2,2-dimethylbutane;

2,3-dimethylbutane;

2,3-dimethylpentane;

2-methylhexane;

3-methylhexane;

2-methylpentane;

3-ethylpentane;

3-methylpentane;

cyclohexane;

cyclopentane;

n-heptane;

methylcyclopentane;

n-pentane; and

n-hexane.

The present invention further relates to the above listed compositions specifically for use in refrigeration or air-conditioning systems employing a centrifugal compressor; a multi-stage or 2-stage centrifugal compressor; or a single pass/single slab heat exchanger.

The present invention further relates to processes for producing refrigeration, heat, and transfer of heat from a heat source to a heat sink using the present inventive compositions.

DETAILED DESCRIPTION OF THE INVENTION

The refrigerant and heat transfer fluid compositions of the present invention comprise at least one hydrocarbon. The refrigerant and heat transfer fluid compositions of the present invention may comprise a single hydrocarbon or may be a combination or mixture comprising more than one hydrocarbon.

The hydrocarbons of the present invention comprise compounds containing hydrogen and carbon. Such hydrocarbons may be straight chain, branched chain or cyclic compounds and have from about 5 to about 10 carbon atoms. Preferred hydrocarbons have from 5 to 7 carbon atoms. Representative hydrocarbons of the present invention are listed in Table 1.

TABLE 1 CAS Chemical Name Chemical Formula Reg. No. 2,2- CH₃CH₂C(CH₃)₃ 75-83-2 dimethylbutane 2,3- CH₃CH(CH₃)CH(CH₃)CH₃ 79-29-8 dimethylbutane 2,3- CH₃CH(CH₃)CH(CH₃)CH₂CH₃ 565-59-3 dimethylpentane 2-methylhexane CH₃CH(CH₃)CH₂CH₂CH₂CH₃ 591-76-4 3-methylhexane CH₃CH₂CH(CH₃)CH₂CH₂CH₃ 589-34-4 2-methylpentane CH₃CH(CH₃)CH₂CH₂CH₃ 107-83-5 3-ethylpentane CH₃CH₂CH(CH₂CH₃)CH₂CH₃ 617-78-7 3-methylpentane CH₃CH₂CH(CH₃)CH₂CH₃ 96-14-0 cyclohexane cyclo-CH₂CH₂CH₂CH₂CH₂CH₂CH₂— 110-82-7 cyclopentane cyclo-CH₂CH₂CH₂CH₂CH₂CH₂— 287-92-3 n-heptane CH₃CH₂CH₂CH₂CH₂CH₂CH₃ 142-82-5 methyl- cyclo-CH₂CH(CH₃)CH₂CH₂CH₂— 96-37-7 cyclopentane n-pentane CH₃CH₂CH₂CH₂CH₃ 109-66-0 n-hexane CH₃CH₂CH₂CH₂CH₂CH₃ 110-54-3

The compounds listed in Table 1 are available commercially or may be prepared by processes known in the art.

The compositions of the present invention that are mixtures may be prepared by any convenient method to combine the desired amounts of the individual components. A preferred method is to weigh the desired component amounts and thereafter combine the components in an appropriate vessel. Agitation may be used, if desired.

Compositions of the present invention have low or zero ozone depletion potential and low global warming potential. The hydrocarbons of the present invention, alone or in mixtures, will have global warming potentials lower than many HFC refrigerants currently in use.

The refrigerant or heat transfer fluid compositions of the present invention include:

-   2,2-dimethylbutane; -   2,3-dimethylbutane; -   2,3-dimethylpentane; -   2-methylhexane; -   3-methylhexane; -   2-methylpentane; -   3-ethylpentane; -   3-methylpentane; -   cyclohexane; -   cyclopentane; -   n-heptane; -   methylcyclopentane; -   n-pentane; -   n-hexane; or -   combinations thereof.

The compositions of the present invention may further comprise about 0.01 weight percent to about 5 weight percent of a stabilizer, free radical scavenger or antioxidant. Such additives include but are not limited to, nitromethane, hindered phenols, hydroxylamines, thiols, phosphites, or lactones. Single additives or combinations may be used.

The compositions of the present invention may further comprise about 0.01 weight percent to about 5 weight percent of a water scavenger (drying compound). Such water scavengers may comprise ortho esters such as trimethyl-, triethyl-, or tripropylorthoformate.

The compositions of the present invention may further comprise an ultra-violet (UV) dye and optionally a solubilizing agent. The UV dye is a useful component for detecting leaks of the refrigerant and heat transfer fluid compositions by permitting one to observe the fluorescence of the dye in the refrigerant or heat transfer fluid compositions at a leak point or in the vicinity of refrigeration or air-conditioning apparatus. One may observe the fluorescence of the dye under an ultra-violet light. Solubilizing agents may be needed to increase solubility of such UV dyes in some refrigerants and heat transfer fluids.

By “ultra-violet” dye is meant a UV fluorescent composition that absorbs light in the ultra-violet or “near” ultra-violet region of the electromagnetic spectrum. The fluorescence produced by the UV fluorescent dye under illumination by a UV light that emits radiation with wavelength anywhere from 10 nanometer to 750 nanometer may be detected. Therefore, if refrigerant or heat transfer fluid containing such a UV fluorescent dye is leaking from a given point in a refrigeration or air-conditioning apparatus, the fluorescence can be detected at the leak point. Such UV fluorescent dyes include but are not limited to naphthalimides, perylenes, coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes, naphthoxanthenes, fluoresceins, and derivatives or combinations thereof. Solubilizing agents of the present invention comprise at least one compound selected from the group consisting of hydrocarbons, hydrocarbon ethers, polyoxyalkylene glycol ethers, amides, nitriles, ketones, chlorocarbons, esters, lactones, aryl ethers, fluoroethers and 1,1,1-trifluoroalkanes.

Hydrocarbon solubilizing agents of the present invention comprise hydrocarbons including straight chained, branched chain or cyclic alkanes or alkenes containing 16 or fewer carbon atoms and only hydrogen with no other functional groups. Representative hydrocarbon solubilizing agents comprise propane, propylene, cyclopropane, n-butane, isobutane, n-pentane, octane, decane, and hexadecane. It should be noted that the refrigerant and the solubilizing agent may not be the same hydrocarbon.

Hydrocarbon ether solubilizing agents of the present invention comprise ethers containing only carbon, hydrogen and oxygen, such as dimethyl ether (DME).

Polyoxyalkylene glycol ether solubilizing agents of the present invention are represented by the formula R¹[(OR²)_(x)OR³]_(y), wherein x is an integer from 1-3; y is an integer from 1-4; R¹ is selected from hydrogen and aliphatic hydrocarbon radicals having 1 to 6 carbon atoms and y bonding sites; R² is selected from aliphatic hydrocarbylene radicals having from 2 to 4 carbon atoms; R³ is selected from hydrogen, and aliphatic and alicyclic hydrocarbon radicals having from 1 to 6 carbon atoms; at least one of R¹ and R³ is selected from said hydrocarbon radical; and wherein said polyoxyalkylene glycol ethers have a molecular weight of from about 100 to about 300 atomic mass units. As used herein, bonding sites mean radical sites available to form covalent bonds with other radicals. Hydrocarbylene radicals mean divalent hydrocarbon radicals.

In the present invention, preferable polyoxyalkylene glycol ether solubilizing agents are represented by R¹[(OR²)_(x)OR³]_(y) wherein x is preferably 1-2; y is preferably 1; R¹ and R³ are preferably independently selected from hydrogen and aliphatic hydrocarbon radicals having 1 to 4 carbon atoms; R² is preferably selected from aliphatic hydrocarbylene radicals having from 2 or 3 carbon atoms, most preferably 3 carbon atoms; the polyoxyalkylene glycol ether molecular weight is preferably from about 100 to about 250 atomic mass units, most preferably from about 125 to about 250 atomic mass units. The R¹ and R³ hydrocarbon radicals having 1 to 6 carbon atoms may be linear, branched or cyclic. Representative R¹ and R³ hydrocarbon radicals include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, and cyclohexyl. Where free hydroxyl radicals on the present polyoxyalkylene glycol ether solubilizing agents may be incompatible with certain compression refrigeration apparatus materials of construction (e.g. Mylar®), R¹ and R³ are preferably aliphatic hydrocarbon radicals having 1 to 4 carbon atoms, most preferably 1 carbon atom. The R² aliphatic hydrocarbylene radicals having from 2 to 4 carbon atoms form repeating oxyalkylene radicals —(OR²)_(x)— that include oxyethylene radicals, oxypropylene radicals, and oxybutylene radicals. The oxyalkylene radical comprising R² in one polyoxyalkylene glycol ether solubilizing agent molecule may be the same, or one molecule may contain different R² oxyalkylene groups. The present polyoxyalkylene glycol ether solubilizing agents preferably comprise at least one oxypropylene radical. Where R¹ is an aliphatic or alicyclic hydrocarbon radical having 1 to 6 carbon atoms and y bonding sites, the radical may be linear, branched or cyclic. Representative R¹ aliphatic hydrocarbon radicals having two bonding sites include, for example, an ethylene radical, a propylene radical, a butylene radical, a pentylene radical, a hexylene radical, a cyclopentylene radical and a cyclohexylene radical. Representative R¹ aliphatic hydrocarbon radicals having three or four bonding sites include residues derived from polyalcohols, such as trimethylolpropane, glycerin, pentaerythritol, 1,2,3-trihydroxycyclohexane and 1,3,5-trihydroxycyclohexane, by removing their hydroxyl radicals.

Representative polyoxyalkylene glycol ether solubilizing agents include but are not limited to: CH₃OCH₂CH(CH₃)O(H or CH₃) (propylene glycol methyl (or dimethyl) ether), CH₃O[CH₂CH(CH₃)O]₂(H or CH₃) (dipropylene glycol methyl (or dimethyl) ether), CH₃O[CH₂CH(CH₃)O]₃(H or CH₃) (tripropylene glycol methyl (or dimethyl) ether), C₂H₅OCH₂CH(CH₃)O(H or C₂H₅) (propylene glycol ethyl (or diethyl) ether), C₂H₅O[CH₂CH(CH₃)O]₂(H or C₂H₅) (dipropylene glycol ethyl (or diethyl) ether), C₂H₅O[CH₂CH(CH₃)O]₃(H or C₂H₅) (tripropylene glycol ethyl (or diethyl) ether), C₃H₇OCH₂CH(CH₃)O(H or C₃H₇) (propylene glycol n-propyl (or di-n-propyl) ether), C₃H₇O[CH₂CH(CH₃)O]₂(H or C₃H₇) (dipropylene glycol n-propyl (or di-n-propyl) ether), C₃H₇O[CH₂CH(CH₃)O]₃(H or C₃H₇) (tripropylene glycol n-propyl (or di-n-propyl) ether), C₄H₉OCH₂CH(CH₃)OH (propylene glycol n-butyl ether), C₄H₉O[CH₂CH(CH₃)O]₂(H or C₄H₉) (dipropylene glycol n-butyl (or di-n-butyl) ether), C₄H₉O[CH₂CH(CH₃)O]₃(H or C₄H₉) (tripropylene glycol n-butyl (or di-n-butyl) ether), (CH₃)₃COCH₂CH(CH₃)OH (propylene glycol t-butyl ether), (CH₃)₃CO[CH₂CH(CH₃)O]₂(H or (CH₃)₃) (dipropylene glycol t-butyl (or di-t-butyl)ether), (CH₃)₃CO[CH₂CH(CH₃)O]₃(H or (CH₃)₃) (tripropylene glycol t-butyl (or di-t-butyl) ether), C₅H₁₁OCH₂CH(CH₃)OH (propylene glycol n-pentyl ether), C₄H₉OCH₂CH(C₂H₅)OH (butylene glycol n-butyl ether), C₄H₉O[CH₂CH(C₂H₅)O]₂H (dibutylene glycol n-butyl ether), trimethylolpropane tri-n-butyl ether (C₂H₅C(CH₂O(CH₂)₃CH₃)₃) and trimethylolpropane di-n-butyl ether (C₂H₅C(CH₂OC(CH₂)₃CH₃)₂CH₂OH).

Amide solubilizing agents of the present invention comprise those represented by the formulae R¹C(O)NR²R³ and cyclo-[R⁴C(O)N(R⁵)—], wherein R¹, R², R³ and R⁵ are independently selected from aliphatic and alicyclic hydrocarbon radicals having from 1 to 12 carbon atoms; R⁴ is selected from aliphatic hydrocarbylene radicals having from 3 to 12 carbon atoms; and wherein said amides have a molecular weight of from about 100 to about 300 atomic mass units. The molecular weight of said amides is preferably from about 160 to about 250 atomic mass units. R¹, R², R³ and R⁵ may optionally include substituted hydrocarbon radicals, that is, radicals containing non-hydrocarbon substituents selected from halogens (e.g., fluorine, chlorine) and alkoxides (e.g. methoxy). R¹, R², R³ and R⁵ may optionally include heteroatom-substituted hydrocarbon radicals, that is, radicals, which contain the atoms nitrogen (aza-), oxygen (oxa-) or sulfur (thia-) in a radical chain otherwise composed of carbon atoms. In general, no more than three non-hydrocarbon substituents and heteroatoms, and preferably no more than one, will be present for each 10 carbon atoms in R¹⁻³, and the presence of any such non-hydrocarbon substituents and heteroatoms must be considered in applying the aforementioned molecular weight limitations. Preferred amide solubilizing agents consist of carbon, hydrogen, nitrogen and oxygen. Representative R¹, R², R³ and R⁵ aliphatic and alicyclic hydrocarbon radicals include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and their configurational isomers. A preferred embodiment of amide solubilizing agents are those wherein R⁴ in the aforementioned formula cyclo-[R⁴C(O)N(R⁵)—] may be represented by the hydrocarbylene radical (CR⁶R⁷)_(n), in other words, the formula cyclo-[(CR⁶R⁷)_(n)C(O)N(R⁵)—] wherein the previously-stated values for molecular weight apply; n is an integer from 3 to 5; R⁵ is a saturated hydrocarbon radical containing 1 to 12 carbon atoms; R⁶ and R⁷ are independently selected (for each n) by the rules previously offered defining R¹⁻³. In the lactams represented by the formula: cyclo-[(CR⁶R⁷)_(n)C(O)N(R⁵)—], all R⁶ and R⁷ are preferably hydrogen, or contain a single saturated hydrocarbon radical among the n methylene units, and R⁵ is a saturated hydrocarbon radical containing 3 to 12 carbon atoms. For example, 1-(saturated hydrocarbon radical)-5-methylpyrrolidin-2-ones.

Representative amide solubilizing agents include but are not limited to: 1-octylpyrrolidin-2-one, 1-decylpyrrolidin-2-one, 1-octyl-5-methylpyrrolidin-2-one, 1-butylcaprolactam, 1-cyclohexylpyrrolidin-2-one, 1-butyl-5-methylpiperid-2-one, 1-pentyl-5-methylpiperid-2-one, 1-hexylcaprolactam, 1-hexyl-5-methylpyrrolidin-2-one, 5-methyl-1-pentylpiperid-2-one, 1,3-dimethylpiperid-2-one, 1-methylcaprolactam, 1-butyl-pyrrolidin-2-one, 1,5-dimethylpiperid-2-one, 1-decyl-5-methylpyrrolidin-2-one, 1-dodecylpyrrolid-2-one, N,N-dibutylformamide and N,N-diisopropylacetamide.

Ketone solubilizing agents of the present invention comprise ketones represented by the formula R¹C(O)R², wherein R¹ and R² are independently selected from aliphatic, alicyclic and aryl hydrocarbon radicals having from 1 to 12 carbon atoms, and wherein said ketones have a molecular weight of from about 70 to about 300 atomic mass units. R¹ and R² in said ketones are preferably independently selected from aliphatic and alicyclic hydrocarbon radicals having 1 to 9 carbon atoms. The molecular weight of said ketones is preferably from about 100 to 200 atomic mass units. R¹ and R² may together form a hydrocarbylene radical connected and forming a five, six, or seven-membered ring cyclic ketone, for example, cyclopentanone, cyclohexanone, and cycloheptanone. R¹ and R² may optionally include substituted hydrocarbon radicals, that is, radicals containing non-hydrocarbon substituents selected from halogens (e.g., fluorine, chlorine) and alkoxides (e.g. methoxy). R¹ and R² may optionally include heteroatom-substituted hydrocarbon radicals, that is, radicals, which contain the atoms nitrogen (aza-), oxygen (keto-, oxa-) or sulfur (thia-) in a radical chain otherwise composed of carbon atoms. In general, no more than three non-hydrocarbon substituents and heteroatoms, and preferably no more than one, will be present for each 10 carbon atoms in R¹ and R², and the presence of any such non-hydrocarbon substituents and heteroatoms must be considered in applying the aforementioned molecular weight limitations. Representative R¹ and R² aliphatic, alicyclic and aryl hydrocarbon radicals in the general formula R¹C(O)R² include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and their configurational isomers, as well as phenyl, benzyl, cumenyl, mesityl, tolyl, xylyl and phenethyl.

Representative ketone solubilizing agents include but are not limited to: 2-butanone, 2-pentanone, acetophenone, butyrophenone, hexanophenone, cyclohexanone, cycloheptanone, 2-heptanone, 3-heptanone, 5-methyl-2-hexanone, 2-octanone, 3-octanone, diisobutyl ketone, 4-ethylcyclohexanone, 2-nonanone, 5-nonanone, 2-decanone, 4-decanone, 2-decalone, 2-tridecanone, dihexyl ketone and dicyclohexyl ketone.

Nitrile solubilizing agents of the present invention comprise nitriles represented by the formula R¹CN, wherein R¹ is selected from aliphatic, alicyclic or aryl hydrocarbon radicals having from 5 to 12 carbon atoms, and wherein said nitriles have a molecular weight of from about 90 to about 200 atomic mass units. R¹ in said nitrile solubilizing agents is preferably selected from aliphatic and alicyclic hydrocarbon radicals having 8 to 10 carbon atoms. The molecular weight of said nitrile solubilizing agents is preferably from about 120 to about 140 atomic mass units. R¹ may optionally include substituted hydrocarbon radicals, that is, radicals containing non-hydrocarbon substituents selected from halogens (e.g., fluorine, chlorine) and alkoxides (e.g. methoxy). R¹ may optionally include heteroatom-substituted hydrocarbon radicals, that is, radicals, which contain the atoms nitrogen (aza-), oxygen (keto-, oxa-) or sulfur (thia-) in a radical chain otherwise composed of carbon atoms. In general, no more than three non-hydrocarbon substituents and heteroatoms, and preferably no more than one, will be present for each 10 carbon atoms in R¹, and the presence of any such non-hydrocarbon substituents and heteroatoms must be considered in applying the aforementioned molecular weight limitations. Representative R¹ aliphatic, alicyclic and aryl hydrocarbon radicals in the general formula R¹CN include pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and their configurational isomers, as well as phenyl, benzyl, cumenyl, mesityl, tolyl, xylyl and phenethyl. Representative nitrile solubilizing agents include but are not limited to: 1-cyanopentane, 2,2-dimethyl-4-cyanopentane, 1-cyanohexane, 1-cyanoheptane, 1-cyanooctane, 2-cyanooctane, 1-cyanononane, 1-cyanodecane, 2-cyanodecane, 1-cyanoundecane and 1-cyanododecane.

Chlorocarbon solubilizing agents of the present invention comprise chlorocarbons represented by the formula RCl_(x), wherein x is 1 or 2; R is selected from aliphatic and alicyclic hydrocarbon radicals having 1 to 12 carbon atoms; and wherein said chlorocarbons have a molecular weight of from about 100 to about 200 atomic mass units. The molecular weight of said chlorocarbon solubilizing agents is preferably from about 120 to 150 atomic mass units. Representative R aliphatic and alicyclic hydrocarbon radicals in the general formula RCl_(x) include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and their configurational isomers.

Representative chlorocarbon solubilizing agents include but are not limited to: 3-(chloromethyl)pentane, 3-chloro-3-methylpentane, 1-chlorohexane, 1,6-dichlorohexane, 1-chloroheptane, 1-chlorooctane, 1-chlorononane, 1-chlorodecane, and 1,1,1-trichlorodecane.

Ester solubilizing agents of the present invention comprise esters represented by the general formula R¹C(O)OR², wherein R¹ and R² are independently selected from linear and cyclic, saturated and unsaturated, alkyl and aryl radicals. Preferred esters consist essentially of the elements C, H and O, have a molecular weight of from about 80 to about 550 atomic mass units.

Representative esters include but are not limited to: (CH₃)₂CHCH₂O(O)C(CH₂)₂₋₄(O)COCH₂CH(CH₃)₂ (diisobutyl dibasic ester), ethyl hexanoate, ethyl heptanoate, n-butyl propionate, n-propyl propionate, ethyl benzoate, di-n-propyl phthalate, benzoic acid ethoxyethyl ester, dipropyl carbonate, “Exxate 700” (a commercial C₇ alkyl acetate), “Exxate 800” (a commercial C₈ alkyl acetate), dibutyl phthalate, and tert-butyl acetate.

Lactone solubilizing agents of the present invention comprise lactones represented by structures [A], [B], and [C]:

These lactones contain the functional group —C(O)O— in a ring of six (A), or preferably five atoms (B), wherein for structures [A] and [B], R₁ through R₈ are independently selected from hydrogen or linear, branched, cyclic, bicyclic, saturated and unsaturated hydrocarbyl radicals. Each R₁ through R₈ may be connected forming a ring with another R₁ through R₈. The lactone may have an exocyclic alkylidene group as in structure [C], wherein R₁ through R₆ are independently selected from hydrogen or linear, branched, cyclic, bicyclic, saturated and unsaturated hydrocarbyl radicals. Each R₁ though R₆ may be connected forming a ring with another R₁ through R₆. The lactone solubilizing agents have a molecular weight range of from about 80 to about 300 atomic mass units, preferred from about 80 to about 200 atomic mass units.

Representative lactone solubilizing agents include but are not limited to the compounds listed in Table 2.

TABLE 2 Molecular Molecular Additive Molecular Structure Formula Weight (amu) (E,Z)-3-ethylidene-5-methyl-dihydro-furan-2-one

C₇H₁₀O₂ 126 (E,Z)-3-propylidene-5-methyl-dihydro-furan-2-one

C₈H₁₂O₂ 140 (E,Z)-3-butylidene-5-methyl-dihydro-furan-2-one

C₉H₁₄O₂ 154 (E,Z)-3-pentylidene-5-methyl-dihydro-furan-2-one

C₁₀H₁₆O₂ 168 (E,Z)-3-Hexylidene-5-methyl-dihydro-furan-2-one

C₁₁H₁₈O₂ 182 (E,Z)-3-Heptylidene-5-methyl-dihydro-furan-2-one

C₁₂H₂₀O₂ 196 (E,Z)-3-octylidene-5-methyl-dihydro-furan-2-one

C₁₃H₂₂O₂ 210 (E,Z)-3-nonylidene-5-methyl-dihydro-furan-2-one

C₁₄H₂₄O₂ 224 (E,Z)-3-decylidene-5-methyl-dihydro-furan-2-one

C₁₅H₂₆O₂ 238 (E,Z)-3-(3,5,5-trimethylhexylidene)-5-methyl-dihydrofuran-2-one

C₁₄H₂₄O₂ 224 (E,Z)-3-cyclohexytmethylidene-5-methyl-dihydrofuran-2-one

C₁₂H₁₈O₂ 194 gamma-octalactone

C₈H₁₄O₂ 142 gamma-nonalactone

C₉H₁₆O₂ 156 gamma-decalactone

C₁₀H₁₈O₂ 170 gamma-undecalactone

C₁₁H₂₀O₂ 184 gamma-dodecalactone

C₁₂H₂₂O₂ 198 3-hexyldihydro-furan-2-one

C₁₀H₁₈O₂ 170 3-heptyldihydro-furan-2-one

C₁₁H₂₀O₂ 184 cis-3-ethyl-5-methyl-dihydro-furan-2-one

C₇H₁₂O₂ 128 cis-(3-propyl-5-methyl)-dihydro-furan-2-one

C₈H₁₄O₂ 142 cis-(3-butyl-5-methyl)-dihydro-furan-2-one

C₉H₁₆O₂ 156 cis-(3-pentyl-5-methyl)-dihydro-furan-2-one

C₁₀H₁₈O₂ 170 cis-3-hexyl-5-methyl-dihydro-furan-2-one

C₁₁H₂₀O₂ 184 cis-3-heptyl-5-methyl-dihydro-furan-2-one

C₁₂H₂₂O₂ 198 cis-3-octyl-5-methyl-dihydro-furan-2-one

C₁₃H₂₄O₂ 212 cis-3-(3,5,5-trimethylhexyl)-5-methyl-dihydro-furan-2-one

C₁₄H₂₆O₂ 226 cis-3-cyclohexylmethyl-5-methyl-dihydro-furan-2-one

C₁₂H₂₀O₂ 196 5-methyl-5-hexyl-dihydro-furan-2-one

C₁₁H₂₀O₂ 184 5-methyl-5-octyl-dihydro-furan-2-one

C₁₃H₂₄O₂ 212 Hexahydro-isobenzofuran-1-one

C₈H₁₂O₂ 140 delta-decalactone

C₁₀H₁₈O₂ 170 delta-undecalactone

C₁₁H₂₀O₂ 184 delta-dodecalactone

C₁₂H₂₂O₂ 198 mixture of 4-hexyl-dihydrofuran-2-one and 3-hexyl-dihydro-furan-2-one

C₁₀H₁₈O₂ 170

Lactone solubilizing agents generally have a kinematic viscosity of less than about 7 centistokes at 40° C. For instance, gamma-undecalactone has kinematic viscosity of 5.4 centistokes and cis-(3-hexyl-5-methyl)dihydrofuran-2-one has viscosity of 4.5 centistokes, both at 40° C. Lactone solubilizing agents may be available commercially or prepared by methods as described in U.S. patent application Ser. No. 10/910,495, filed Aug. 3, 2004, incorporated herein by reference.

Aryl ether solubilizing agents of the present invention comprise aryl ethers represented by the formula R¹OR², wherein: R¹ is selected from aryl hydrocarbon radicals having from 6 to 12 carbon atoms; R² is selected from aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms; and wherein said aryl ethers have a molecular weight of from about 100 to about 150 atomic mass units. Representative R¹ aryl radicals in the general formula R¹OR² include phenyl, biphenyl, cumenyl, mesityl, tolyl, xylyl, naphthyl and pyridyl. Representative R² aliphatic hydrocarbon radicals in the general formula R¹OR² include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl. Representative aromatic ether solubilizing agents include but are not limited to: methyl phenyl ether (anisole), 1,3-dimethyoxybenzene, ethyl phenyl ether and butyl phenyl ether.

Fluoroether solubilizing agents of the present invention comprise those represented by the general formula R¹OCF₂CF₂H, wherein R¹ is selected from aliphatic, alicyclic, and aromatic hydrocarbon radicals having from about 5 to about 15 carbon atoms, preferably primary, linear, saturated, alkyl radicals. Representative fluoroether solubilizing agents include but are not limited to: C₈H₁₇OCF₂CF₂H and C₆H₁₃OCF₂CF₂H. It should be noted that if the refrigerant is a fluoroether, then the solubilizing agent may not be the same fluoroether.

Fluoroether solubilizing agents may further comprise ethers derived from fluoro-olefins and polyols. The fluoro-olefins may be of the type CF₂═CXY, wherein X is hydrogen, chlorine or fluorine, and Y is chlorine, fluorine, CF₃ or OR_(f), wherein R_(f) is CF₃, C₂F₅, or C₃F₇. Representative fluoro-olefins are tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoromethylvinyl ether. The polyols may be linear or branched. Linear polyols may be of the type HOCH₂ (CHOH)_(x)(CRR′)_(y)CH₂OH, wherein R and R′ are hydrogen, or CH₃, or C₂H₅ and wherein x is an integer from 0-4, and y is an integer from 0-4. Branched polyols may be of the type C(OH)_(t)(R)_(u)(CH2OH)_(v)[(CH2)_(m)CH2OH]_(w), wherein R may be hydrogen, CH₃ or C₂H₅, m may be an integer from 0 to 3, t and u may be 0 or 1, v and w are integers from 0 to 4, and also wherein t+u+v+w=4. Representative polyols are trimethylol propane, pentaerythritol, butanediol, and ethylene glycol.

1,1,1-Trifluoroalkane solubilizing agents of the present invention comprise 1,1,1-trifluoroalkanes represented by the general formula CF₃R¹, wherein R¹ is selected from aliphatic and alicyclic hydrocarbon radicals having from about 5 to about 15 carbon atoms, preferably primary, linear, saturated alkyl radicals. Representative 1,1,1-trifluoroalkane solubilizing agents include but are not limited to: 1,1,1-trifluorohexane and 1,1,1-trifluorododecane.

Solubilizing agents of the present invention may be present as a single compound, or may be present as a mixture of more than one solubilizing agent. Mixtures of solubilizing agents may contain two solubilizing agents from the same class of compounds, say two lactones, or two solubilizing agents from two different classes, such as a lactone and a polyoxyalkylene glycol ether.

In the present compositions comprising refrigerant and UV fluorescent dye, or comprising heat transfer fluid and UV fluorescent dye, from about 0.001 weight percent to about 1.0 weight percent of the compositions is UV dye, preferably from about 0.005 weight percent to about 0.5 weight percent, and most preferably from 0.01 weight percent to about 0.25 weight percent.

Solubility of these UV fluorescent dyes in refrigerants and heat transfer fluids may be poor. Therefore, methods for introducing these dyes into the refrigeration or air-conditioning apparatus have been awkward, costly and time consuming. U.S. Pat. No. RE 36,951 describes a method, which utilizes a dye powder, solid pellet or slurry of dye that may be inserted into a component of the refrigeration or air-conditioning apparatus. As refrigerant and lubricant are circulated through the apparatus, the dye is dissolved or dispersed and carried throughout the apparatus. Numerous other methods for introducing dye into a refrigeration or air-conditioning apparatus are described in the literature.

Ideally, the UV fluorescent dye could be dissolved in the refrigerant itself thereby not requiring any specialized method for introduction to the refrigeration or air-conditioning apparatus. The present invention relates to compositions including UV fluorescent dye, which may be introduced into the system in the refrigerant. The inventive compositions will allow the storage and transport of dye-containing refrigerant and heat transfer fluid even at low temperatures while maintaining the dye in solution.

In the present compositions comprising refrigerant, UV fluorescent dye and solubilizing agent, or comprising heat transfer fluid, UV fluorescent dye and solubilizing agent, from about 1 to about 50 weight percent, preferably from about 2 to about 25 weight percent, and most preferably from about 5 to about 15 weight percent of the combined composition is solubilizing agent in the refrigerant or heat transfer fluid. In the compositions of the present invention the UV fluorescent dye is present in a concentration from about 0.001 weight percent to about 1.0 weight percent in the refrigerant or heat transfer fluid, preferably from 0.005 weight percent to about 0.5 weight percent, and most preferably from 0.01 weight percent to about 0.25 weight percent.

Optionally, commonly used refrigeration or air-conditioning system additives may be added, as desired, to compositions of the present invention in order to enhance performance and system stability. These additives are known in the field of refrigeration and air-cinditioning, and include, but are not limited to, anti wear agents, extreme pressure lubricants, corrosion and oxidation inhibitors, metal surface deactivators, free radical scavengers, and foam control agents. In general, these additives are present in the inventive compositions in small amounts relative to the overall composition. Typically concentrations of from less than about 0.1 weight percent to as much as about 3 weight percent of each additive are used. These additives are selected on the basis of the individual system requirements. These additives include members of the triaryl phosphate family of EP (extreme pressure) lubricity additives, such as butylated triphenyl phosphates (BTPP), or other alkylated triaryl phosphate esters, e.g. Syn-0-Ad 8478 from Akzo Chemicals, tricresyl phosphates and related compounds. Additionally, the metal dialkyl dithiophosphates (e.g. zinc dialkyl dithiophosphate (or ZDDP), Lubrizol 1375 and other members of this family of chemicals may be used in compositions of the present invention. Other antiwear additives include natural product oils and asymmetrical polyhydroxyl lubrication additives, such as Synergol TMS (International Lubricants). Similarly, stabilizers such as anti oxidants, free radical scavengers, and water scavengers may be employed. Compounds in this category can include, but are not limited to, butylated hydroxy toluene (BHT) and epoxides.

Solubilizing agents such as ketones may have an objectionable odor, which can be masked by addition of an odor masking agent or fragrance. Typical examples of odor masking agents or fragrances may include Evergreen, Fresh Lemon, Cherry, Cinnamon, Peppermint, Floral or Orange Peel, all commercially available, as well as d-limonene and pinene. Such odor masking agents may be used at concentrations of from about 0.001% to as much as about 15% by weight based on the combined weight of odor masking agent and solubilizing agent.

The present invention further relates to a method of using the refrigerant or heat transfer fluid compositions further comprising ultraviolet fluorescent dye, and optionally, solubilizing agent, in refrigeration or air-conditioning apparatus. The method comprises introducing the refrigerant or heat transfer fluid composition into the refrigeration or air-conditioning apparatus. This may be done by dissolving the UV fluorescent dye in the refrigerant or heat transfer fluid composition in the presence of a solubilizing agent and introducing the combination into the apparatus. Alternatively, this may be done by combining solubilizing agent and UV fluorescent dye and introducing said combination into refrigeration or air-conditioning apparatus containing refrigerant and/or heat transfer fluid. The resulting composition may be used in the refrigeration or air-conditioning apparatus.

The present invention further relates to a method of using the refrigerant or heat transfer fluid compositions comprising ultraviolet fluorescent dye to detect leaks. The presence of the dye in the compositions allows for detection of leaking refrigerant in the refrigeration or air-conditioning apparatus. Leak detection helps to address, resolve or prevent inefficient operation of the apparatus or system or equipment failure. Leak detection also helps one contain chemicals used in the operation of the apparatus.

The method comprises providing the composition comprising refrigerant and ultra-violet fluorescent dye, or comprising heat transfer fluid and ultra-violet fluorescent dye as described herein, and optionally, a solubilizing agent as described herein, to refrigeration and air-conditioning apparatus and employing a suitable means for detecting the UV fluorescent dye-containing refrigerant. Suitable means for detecting the dye include, but are not limited to, ultra-violet lamp, often referred to as a “black light” or “blue light”. Such ultra-violet lamps are commercially available from numerous sources specifically designed for this purpose. Once the ultra-violet fluorescent dye containing composition has been introduced to the refrigeration or air-conditioning apparatus and has been allowed to circulate throughout the system, a leak can be found by shining said ultra-violet lamp on the apparatus and observing the fluorescence of the dye in the vicinity of any leak point.

The present invention further relates to a method of using the compositions of the present invention for producing refrigeration or heat, wherein the method comprises producing refrigeration by evaporating said composition in the vicinity of a body to be cooled and thereafter condensing said composition; or producing heat by condensing said composition in the vicinity of the body to be heated and thereafter evaporating said composition. Where the composition of the present invention includes refrigeration or heat transfer fluid composition with an ultra-violet fluorescent dye, and/or a solubilizing agent, the refrigerant or heat transfer fluid component of the composition is evaporated and thereafter condensed to produce refrigeration, or condensed and thereafter evaporated to produce heat.

Mechanical refrigeration is primarily an application of thermodynamics wherein a cooling medium, such as a refrigerant, goes through a cycle so that it can be recovered for reuse. Commonly used cycles include vapor-compression, absorption, steam-jet or steam-ejector, and air.

Vapor-compression refrigeration systems include an evaporator, a compressor, a condenser, and an expansion device. A vapor-compression cycle re-uses refrigerant in multiple steps producing a cooling effect in one step and a heating effect in a different step. The cycle can be described simply as follows. Liquid refrigerant enters an evaporator through an expansion device, and the liquid refrigerant boils in the evaporator at a low temperature to form a gas and produce cooling. The low-pressure gas enters a compressor where the gas is compressed to raise its pressure and temperature. The higher-pressure (compressed) gaseous refrigerant then enters the condenser in which the refrigerant condenses and discharges its heat to the environment. The refrigerant returns to the expansion device through which the liquid expands from the higher-pressure level in the condenser to the low-pressure level in the evaporator, thus repeating the cycle.

The present invention further relates to a process for producing cooling comprising evaporating the compositions of the present invention in the vicinity of a body to be cooled, and thereafter condensing said compositions.

The present invention further relates to a process for producing heat comprising condensing the compositions of the present invention in the vicinity of a body to be heated, and thereafter evaporating said compositions.

There are various types of compressors that may be used in refrigeration applications. Compressors can be generally classified as reciprocating, rotary, jet, centrifugal, scroll, screw or axial-flow, depending on the mechanical means to compress the fluid, or as positive-displacement (e.g., reciprocating, scroll or screw) or dynamic (e.g., centrifugal or jet), depending on how the mechanical elements act on the fluid to be compressed.

Either positive displacement or dynamic compressors may be used in the present inventive process. A centrifugal type compressor is the preferred equipment for the present refrigerant compositions.

A centrifugal compressor uses rotating elements to accelerate the refrigerant radially, and typically includes an impeller and diffuser housed in a casing. Centrifugal compressors usually take fluid in at an impeller eye, or central inlet of a circulating impeller, and accelerate it radially outward. Some static pressure rise occurs in the impeller, but most of the pressure rise occurs in the diffuser section of the casing, where velocity is converted to static pressure. Each impeller-diffuser set is a stage of the compressor. Centrifugal compressors are built with from 1 to 12 or more stages, depending on the final pressure desired and the volume of refrigerant to be handled.

The pressure ratio, or compression ratio, of a compressor is the ratio of absolute discharge pressure to the absolute inlet pressure. Pressure delivered by a centrifugal compressor is practically constant over a relatively wide range of capacities.

Positive displacement compressors draw vapor into a chamber, and the chamber decreases in volume to compress the vapor. After being compressed, the vapor is forced from the chamber by further decreasing the volume of the chamber to zero or nearly zero. A positive displacement compressor can build up a pressure, which is limited only by the volumetric efficiency and the strength of the parts to withstand the pressure.

Unlike a positive displacement compressor, a centrifugal compressor depends entirely on the centrifugal force of the high-speed impeller to compress the vapor passing through the impeller. There is no positive displacement, but rather what is called dynamic-compression.

The pressure a centrifugal compressor can develop depends on the tip speed of the impeller. Tip speed is the speed of the impeller measured at its tip and is related to the diameter of the impeller and its revolutions per minute. The capacity of the centrifugal compressor is determined by the size of the passages through the impeller. This makes the size of the compressor more dependent on the pressure required than the capacity.

Because of its high-speed operation, a centrifugal compressor is fundamentally a high volume, low-pressure machine. A centrifugal compressor works best with a low-pressure refrigerant, such as trichlorofluoromethane (CFC-11) or 1,2,2-trichlorotrifluoroethane (CFC-113).

Large centrifugal compressors typically operate at 3000 to 7000 revolutions per minute (rpm). Small turbine centrifugal compressors are designed for high speeds, from about 40,000 to about 70,000 (rpm), and have small impeller sizes, typically less than 0.15 meters (about 6 inches).

A multi-stage impeller may be used in a centrifugal compressor to improve compressor efficiency thus requiring less power in use. For a two-stage system, in operation, the discharge of the first stage impeller goes to the suction intake of a second impeller. Both impellers may operate by use of a single shaft (or axle). Each stage can build up a compression ratio of about 4 to 1; that is, the absolute discharge pressure can be four times the absolute suction pressure. Several examples of two-stage centrifugal compressor systems, particularly for automotive applications, are described in U.S. Pat. No. 5,065,990 and U.S. Pat. No. 5,363,674, both incorporated herein by reference.

The compositions of the present invention suitable for use in a refrigeration, or air-conditioning systems employing a centrifugal compressor comprise at least one of:

2,2-dimethylbutane;

2,3-dimethylbutane;

2,3-dimethylpentane;

2-methylhexane;

3-methylhexane;

2-methylpentane;

3-ethylpentane;

3-methylpentane;

cyclohexane;

cyclopentane;

n-heptane;

methylcyclopentane;

n-pentane; and

n-hexane.

These above-listed compositions are also suitable for use in a multi-stage centrifugal compressor, preferably a two-stage centrifugal compressor apparatus.

The compositions of the present invention may be used in stationary air-conditioning, heat pumps or mobile air-conditioning and refrigeration systems. Stationary air-conditioning and heat pump applications include window, ductless, ducted, packaged terminal, chillers and commercial, including packaged rooftop. Refrigeration applications include domestic or home refrigerators and freezers, ice machines, self-contained coolers and freezers, walk-in coolers and freezers and transport refrigeration systems.

The compositions of the present invention may additionally be used in air-conditioning, heating and refrigeration systems that employ fin and tube heat exchangers, microchannel heat exchangers and vertical or horizontal single pass tube or plate type heat exchangers.

Conventional microchannel heat exchangers may not be ideal for the low pressure refrigerant compositions of the present invention. The low operating pressure and density result in high flow velocities and high frictional losses in all components. In these cases, the evaporator design may be modified. Rather than several microchannel slabs connected in series (with respect to the refrigerant path) a single slab/single pass heat exchanger arrangement may be used. Therefore, a preferred heat exchanger for the low pressure refrigerants of the present invention is a single slab/single pass heat exchanger.

In addition to two-stage or other multi-stage centrifugal compressor apparatus, the following compositions of the present invention are suitable for use in refrigeration or air-conditioning apparatus employing a single slab/single pass heat exchanger:

2,2-dimethylbutane;

2,3-dimethylbutane;

2,3-dimethylpentane;

2-methylhexane;

3-methylhexane;

2-methylpentane;

3-ethylpentane;

3-methylpentane;

cyclohexane;

cyclopentane;

n-heptane;

methylcyclopentane;

n-pentane;

n-hexane; and combinations thereof.

The compositions of the present invention are particularly useful in small turbine centrifugal compressors (mini-centrifugal compressors), which can be used in auto and window air-conditioning, heat pumps, or transport refrigeration, as well as other applications. These high efficiency mini-centrifugal compressors may be driven by an electric motor and can therefore be operated independently of the engine speed. A constant compressor speed allows the system to provide a relatively constant cooling capacity at all engine speeds. This provides an opportunity for efficiency improvements especially at higher engine speeds as compared to a conventional R-134a automobile air-conditioning system. When the cycling operation of conventional systems at high driving speeds is taken into account, the advantage of these low pressure systems becomes even greater.

Alternatively, rather than use electrical power, the mini-centrifugal compressor may be powered by an engine exhaust gas driven turbine or a ratioed gear drive assembly with ratioed belt drive. The electrical power available in current automobile design is about 14 volts, but the new mini-centrifugal compressor requires electrical power of about 50 volts. Therefore, use of an alternative power source would be advantageous. A refrigeration or air-conditioning apparatus powered by an engine exhaust gas driven turbine is described in detail in U.S. provisional patent application No. 60/658,915, filed Mar. 4, 2005, incorporated herein by reference. A refrigeration or air-conditioning apparatus powered by a ratioed gear drive assembly is described in detail in U.S. provisional patent application No. 60/663924, filed Mar. 21, 2005, incorporated herein by reference.

The present invention further relates to a process to produce cooling comprising compressing a composition of the present invention, in a mini-centrifugal compressor powered by an engine exhaust gas driven turbine; condensing said composition; and thereafter evaporating said composition in the vicinity of a body to be cooled.

The present invention further relates to a process to produce cooling comprising compressing a composition of the present invention, in a mini-centrifugal compressor powered by a ratioed gear drive assembly with a ratioed belt drive; condensing said composition; and thereafter evaporating said composition in the vicinity of a body to be cooled.

Some of the low pressure refrigerant fluids of the present invention may be suitable as drop-in replacements for CFC-113 in existing centrifugal equipment.

The present invention further relates to a method for replacing CFC-113 in existing refrigeration apparatus or air-conditioning apparatus, said method comprising providing a composition of the present invention as the replacement.

The present invention further relates to a process for transfer of heat from a heat source to a heat sink wherein the compositions of the present invention serve as heat transfer fluids. Said process for heat transfer comprises transferring the compositions of the present invention from a heat source to a heat sink.

Heat transfer fluids are utilized to transfer, move or remove heat from one space, location, object or body to a different space, location, object or body by radiation, conduction, or convection. A heat transfer fluid may function as a secondary coolant by providing means of transfer for cooling (or heating) from a remote refrigeration (or heating) system. In some systems, the heat transfer fluid may remain in a constant state throughout the transfer process (i.e., not evaporate or condense). Alternatively, evaporative cooling processes may utilize heat transfer fluids as well.

A heat source may be defined as any space, location, object or body from which it is desirable to transfer, move or remove heat. Examples of heat sources may be spaces (open or enclosed) requiring refrigeration or cooling, such as refrigerator or freezer cases in a supermarket, building spaces requiring air-conditioning, or the passenger compartment of an automobile requiring air-conditioning. A heat sink may be defined as any space, location, object or body capable of absorbing heat. A vapor compression refrigeration system is one example of such a heat sink.

EXAMPLES Example 1 Tip Speed to Develop Pressure

Tip speed can be estimated by making some fundamental relationships for refrigeration equipment that use centrifugal compressors. The torque an impeller ideally imparts to a gas is defined as T=m*(v ₂ *r ₂ −v ₁ *r ₁)   Equation 1 where

T=torque, Newton-meters

m=mass rate of flow, kg/sec

v₂=tangential velocity of refrigerant leaving impeller (tip speed), meters/sec

r₂=radius of exit impeller, meters

v₁=tangential velocity of refrigerant entering impeller, meters/sec

r₁=radius of inlet of impeller, meters

Assuming the refrigerant enters the impeller in an essentially axial direction, the tangential component of the velocity v₁=0, therefore T=m*v ₂ *r ₂   Equation 2

The power required at the shaft is the product of the torque and the rotative speed P=T*ω  Equation 3 where

P=power, W

ω=angular velocity, radians/s

therefore, P=T*w=m*v ₂ *r ₂*ω  Equation 4

At low refrigerant flow rates, the tip speed of the impeller and the tangential velocity of the refrigerant are nearly identical; therefore r ₂ *w=v ₂   Equation 5 and P=m*v ₂ *v ₂   Equation 6

Another expression for ideal power is the product of the mass rate of flow and the isentropic work of compression, P=m*H _(i)*(1000 J/kJ)   Equation 7 where

H_(i)=Difference in enthalpy of the refrigerant from a saturated vapor at the evaporating conditions to saturated condensing conditions, kJ/kg.

Combining the two expressions Equation 6 and 7 produces, v ₂ *v ₂=1000*H _(i)   Equation 8

Although Equation 8 is based on some fundamental assumptions, it provides a good estimate of the tip speed of the impeller and provides an important way to compare tip speeds of refrigerants.

The table below shows theoretical tip speeds that are calculated for 1,2,2-trichlorotrifluoroethane (CFC-113) and 3-ethylpentane of the present invention. The conditions assumed for this comparison are:

Evaporator temperature 40.0° F. (4.4° C.) Condenser temperature 110.0° F. (43.3° C.) Liquid subcool temperature 10.0° F. (5.5° C.) Return gas temperature  75.0° F. (23.8° C.) Compressor efficiency is 70%

These are typical conditions under which small turbine centrifugal compressors perform.

TABLE 2 Hi Hi*0.7 Hi*0.7 V2 V2 rel Composition Btu/lb Btu/lb KJ/Kg m/s to CFC-113 CFC-113 10.92 7.6 17.8 133.3 na 3-ethylpentane 14.54 10.2 23.7 153.9 115%

Example 2 Performance Data

The following table shows the performance of various refrigerants compared to CFC-113, by showing evaporator and condenser pressures, compressor discharge temperature, COP (energy efficiency) and capacity (Cap). The data are based on the following conditions.

Evaporator temperature 40.0° F. (4.4° C.) Condenser temperature 110.0° F. (43.3° C.) Subcool temperature 10.0° F. (5.5° C.) Return gas temperature  75.0° F. (23.8° C.) Compressor efficiency is 70%

TABLE 3 Comp Comp Evap Evap Cond Cond Disch Disch Pres Pres Pres Pres Temp Temp Cap Cap Compound (Psia) (kPa) (Psia) (kPa) (F.) (C.) COP (Btu/min) (kW) CFC-113 2.7 19 12.8 88 156.3 69.1 4.18 14.8 0.26 2,2-dimethylbutane 2.7 18 11.8 81 137.8 58.8 4.07 15.4 0.27 2,3-dimethylbutane 1.9 13 8.9 62 138.3 59.1 4.08 11.4 0.20 2,3-dimethylpentane 0.5 3 3.0 21 141.8 61.0 4.15 3.6 0.06 2-methylbutane 6.0 41 23.9 165 146.3 63.5 4.11 32.6 0.57 2-methylhexane 0.5 3 2.9 20 142.3 61.3 4.15 3.4 0.06 2-methylpentane 1.7 11 8.2 57 143.7 62.1 4.14 10.5 0.18 3-ethylpentane 0.4 3 2.6 18 143.1 61.7 4.16 3.0 0.05 3-methylhexane 0.4 3 2.7 19 142.8 61.6 4.15 3.2 0.06 3-methylpentane 1.5 10 7.4 51 144.4 62.4 4.15 9.5 0.17 cyclohexane 0.7 5 4.1 28 151.2 66.2 4.23 5.1 0.09 cyclopentane 2.6 18 11.8 82 155.7 68.7 4.24 16.1 0.28 n-heptane 0.3 2 2.1 14 144.8 62.7 4.17 2.4 0.04 n-hexane 1.1 8 6.1 42 146.2 63.4 4.16 7.6 0.13 methylcyclopentane 1.1 7 5.6 38 149.3 65.2 4.21 7.1 0.12 n-pentane 4.4 30 18.7 129 152.6 67.0 4.17 25.5 0.45

Data show the compositions of the present invention have evaporator and condenser pressures similar to CFC-113. Some compositions also have higher capacity or energy efficiency than CFC-113. 

1. A refrigerant or heat transfer fluid composition consisting of 2,2-dimethylbutane, and at least one ultra-violet fluorescent dye selected from the group consisting of naphthalimides, perylenes, coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes, naphthoxanthenes, fluoresceins, and derivatives thereof.
 2. A method of producing cooling, said method comprising: evaporating the refrigerant or heat transfer fluid component of the composition of claim 1 in the vicinity of a body to be cooled and thereafter condensing said refrigerant or heat transfer fluid component.
 3. The method of claim 2 wherein said method comprises producing said cooling in a refrigeration or air-conditioning apparatus employing a multi-stage centrifugal compressor.
 4. The method of claim 3 wherein said multi-stage centrifugal compressor is a two-stage centrifugal compressor.
 5. A method of producing heat, said method comprising: condensing the refrigerant or heat transfer fluid component of the composition of claim 1 in the vicinity of the body to be heated and thereafter evaporating said refrigerant or heat transfer fluid component.
 6. A process to produce cooling comprising compressing a composition of claim 1 in a mini-centrifugal compressor powered by an engine exhaust gas driven turbine; condensing said composition; and thereafter evaporating said composition in the vicinity of a body to be cooled.
 7. A process to produce cooling comprising compressing a composition of claim 1 in a mini-centrifugal compressor powered by a ratioed gear drive assembly with a ratioed belt drive; condensing said composition; and thereafter evaporating said composition in the vicinity of a body to be cooled.
 8. A refrigerant or heat transfer fluid composition consisting of 2,2-dimethylbutane, at least one ultra-violet fluorescent dye selected from the group consisting of naphthalimides, pervienes, coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes, naphthoxanthenes, fluoresceins, and derivatives thereof and at least one solubilizing agent selected from the group consisting of hydrocarbons, dimethylether, polyoxyalkylene glycol ethers, amides, ketones, nitriles, chlorocarbons, esters, lactones, aryl ethers, fluoroethers, and 1,1,1-trifluoroalkanes; and wherein the refrigerant and solubilizing agent may not be the same compound. 